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Glossary

Internal fixators

The new generation of plates act as “internal fixators”. This is achieved by
locking the screw heads into the plate via a thread in the screw head. In
contrast to conventional plates, these implants fix the fractured fragments in
the determined position without the screws loosening, which could lead to
secondary displacement.

In case of healthy bone structure, monocortical angular stable screws are
applied. As an alternative, bicortical angular stable screws can be chosen,
especially in case of osteoporosis, or a combination of monocortical and
bicortical screws can be chosen.

No direct bone to plate contact

A second advantage of the new angular stable plates is that they do not
require firm contact and pressure between plate and bone surface for stability.
Even when placed distant to the bone, their fixation strength is superior to
conventional plates. This means that blood flow in the periosteum is less
compromised than in open conventional procedures.

Load bearing

Anatomy

The medial plateau is the larger of the two articular surfaces and is
concave in both transverse planes. The lateral plateau is smaller and convex
and lies slightly higher than the medial joint surface, which helps in
identifying it on the lateral x-ray.

Superficial peroneal nerve

A slightly elongated distal incision is useful both to check plate location
and avoid damage to the superficial peroneal nerve. The nerve crosses the tibia
in the proximity of the distal part of the 13-hole plate (be careful with short
stature patient where this can happen even with a nine hole plate).

Compartment syndrome

Monitor the neurovascular status of the limb carefully not to miss a compartment syndrome.

Anatomical reduction first

Anatomical reduction of the articular surface is mandatory before fixation of the metaphyseal fracture fragment.

Not all complete articular fractures can be perfectly reduced through a medial and/or a lateral approach. Sometimes fractures with a flexion injury mechanism need to be approached posteriorly as well.

Plate lengthGenerally speaking, the plates for the bridging technique should be rather long in order to distribute the forces, as well as to provide relative stability

The preoperative x-ray planning template is useful in determining the length of the LISS plate and the position of the screws.

Number of screwsIn case of healthy bone structure, five well placed monocortical angular stable screws are applied to secure the LISS to the tibial shaft. As an alternative, three bicortical angular stable screws can be chosen, and are recommended in patients with osteoporosis.
If LISS with “combi” holes is used, regular screws opposed to angular stable screws can be used in good bone stock. In this case four regular bicortical screws were used in the distal fracture fragment.

See also
Gautier E, Sommer C (2003) Guidelines for the clinical application of the LCP. Injury 34(Suppl 2):B63-76. Review

Approach for minimally invasive osteosynthesis (MIO)

Anterolateral approach

Single or double distractor

Fracture reduction techniques in the proximal tibia rely on the concept of
indirect reduction to realign the fracture fragments where one relies on
ligamentotaxis, that is the attachment of soft-tissue hinges such as ligaments
and muscle. These techniques require the use of one or two large distractors
bridging the slightly flexed knee. Ligamentotaxis can reduce a considerable
portion of the fracture, primarily large condylar fragments, as well as realign
the diaphyseal-metaphyseal shaft extension of the fracture.

Elevation of the impacted articular surface

The impacted articular fragments must be elevated gently with a pusher which
can be introduced through the fracture or by creating a small cortical window.
It is most important that the defect in the metaphysis which is created by the
reduction of the impacted articular fragments be filled with a bone graft to
prevent secondary collapse of the reduced articular fragments. Alternatively,
bone substitute can be used.

Preliminary fixation of the articular surface

Fixation of the articular surface

In simple fracture patterns lag screws are used to achieve absolute stability; whereas in complex fracture patterns, compression must be avoided. In complex fractures we use positioning screws to secure fixation of the articular fragments..

Additional implants such as lag screws should not compromise the subsequent application of the LISS plate. To avoid this, lag screws can be inserted through stab wounds from the medial side.

It should be noted that LISS is very effective for the fixation of metaphyseal region. However, for the articular surface, the locking screw only supports the anterior 2/3 of the plateau. Additional fixation is recommended if there is an independent intra-articular fracture in the posterior column.Note: Care should be taken not to place the screws too close to the subchondral bone to prevent excessive stiffening and possible damage to the overlying articular cartilage.

Use external distractor

LISS insertion

Once the LISS has been assembled and fixed to the guide handle with the
fixation bolt and stabilization sleeve inserted through the hole C of the guide
you are ready to insert the internal fixator onto the bone.

Insert the assembled internal fixator between the anterior tibial muscle and
the periosteum in the epiperiosteal space. The LISS plate is slid in the distal
direction, with its distal end in constant contact with the bone. The proximal
end of the plate is positioned against the lateral condyle. The correct
position of the LISS on the condyle is checked carefully.

Building a frame - make a small incision over the most distal hole

Once the LISS is properly aligned with the bone, the drill sleeve is removed
from hole labeled “C”. Next insert the drill sleeve and trocar though the most
distal hole of the drill guide depending on the length of plate you have chosen
(5,9, or 13). Before you can reach the plate with the drill sleeve and trocar
you must must make a stab incision. If you are using a long plate (9 in a short
individual or 13 in a normal individual) dissect down to the plate to avoid
injuring the superficial peroneal nerve. Once all is secure insert the drill
sleeve and trocar and secure the drill sleeve to the guide handle. Remove the
trocar and replace it with the fixation bolt which you thread into the plate.
This completes the building of the frame.

You must check the position of the LISS with the image intensifier in both
the AP and lateral position.

Be aware of the superficial peroneal nerve

If a 13-hole LISS plate is being used or a 9 hole in a short stature
individual, careful soft-tissue dissection has to be carried out down to the
plate before inserting the trocar and drill sleeve, in order to visualize the
superficial peroneal nerve. Once all is secure the position of the drill sleeve
is held securely by tightening the fixation screw on the insertion guide. The
trocar is then replaced with the stabilization bolt. The stabilization bolt is
threaded into the LISS plate to close the frame.

It should be noted that once the bolt has been inserted, it becomes
difficult to change the position of the plate–guide assembly, due to the soft
tissues around the stabilization bolt.

Preliminary fixation of the LISS

For preliminary fixation of the internal fixator, 2.0 mm K-wires are
inserted through the most proximal K-wire hole on the insertion guide (guided
only through the aluminum foot part of the insertion guide) and through the
stabilization bolt in the most distal hole of the LISS.

Pitfall: check proper plate alignment of the LISS on the lateral tibial shaft in both the AP and lateral projection

Before fixing the LISS to the bone with the screws in the shaft area, check
if they all are in a central position in the lateral cortex. In the event of an
eccentric position, there is substantial risk of implant failure with loss of
fixation due to the fact that eccentrically inserted screws have a markedly
reduced fixation strength. This applies especially to monocortical screws.

General considerations

Screw placement depends on the type of fracture. The positions of the locking head screws should be chosen in accordance with the established biomechanical principles for internal fixation. The locking head screws should be inserted remote from the fracture gap in the main diaphyseal fragment. Three to four plate holes in the region of the fracture zone should remain free of screws to ensure sufficient elasticity of the construct.

It should be noted that once the initial locking head screws have been inserted into each main fragment, length and rotation are fixed. Antecurvatum and recurvatum deformities can still be adjusted within narrow limits. For this reason, it is recommended to start by inserting the first locking head screw in the proximal fragment.
If a screw has to be removed and reinserted, the hand torque limiting screwdriver should be used and not the power tool.

Measuring of screw length for proximal fragment
Use the measuring device with a 2.0 mm K-wire of 280 mm length, placed through the centering sleeve in the drill sleeve. This will allow you to determine the appropriate screw length. Using image intensification, the K-wire is pushed to the desired depth, leaving at least 5 mm between the tip of the K-wire and the medial cortex. The screw length is measured over the K-wire using the measuring device for K-wires while the guide sleeve in place. The length is rounded down to the nearest screw length. This will
ensure that the tip of the screw will not protrude through the medial cortex.

Insertion of locking head screw in the articular block

To improve visualization of the condyle, the drill sleeves for the two most
proximal holes are guided through the aluminum foot part of the insertion guide
only. To prevent rotation of the drill sleeve, it is therefore necessary to
hold it with two fingers during insertion or removal of the K-wire, as well as
during insertion or removal of the two most proximal screws.

Pearl: fine tuning of the reduction

The shaft fragment has a tendency to drift away from the plate. To fine tune
the reduction or the approximation of the LISS to the bone, the Whirlybird may
be used. It has a sliding nut on its proximal end which can be tightened
against the insertion guide, thus approximating or docking the bone to the
LISS.

Insertion of the first distal locking head screw

The image intensifier should be oriented obliquely to allow accurate
visualization of the point at which the K-wire exits anteromedially or
posteromedially.

26 mm or 18 mm locking head screw should be used in the shaft region.

Initially, a stab incision is made and the trocar is inserted through the
drill sleeve.

Battery-driven or compressed-air tools are used to insert the self-drilling,
self-tapping locking head screw, as only these tools provide the required drill
speed.

It is also important to cool the locking head screws with saline solution
through the drill sleeve during the drilling procedure, to prevent thermal
necrosis. The insertion sleeves have a side nipple to allow irrigation. Use
standard tubing and syringes with saline solution.

Both the screwdriver shaft and the torque-limiting screwdriver are equipped
with a self-holding mechanism. Slight pressure should be used to ensure that
the screwdriver shaft penetrates the socket of the screw head on pick-up.

In case the whirlybird technique was used, the first distal locking head
screw should be inserted next to it.

Note: torque-limiting screwdriverFor the final tightening the torque-limiting screwdriver has to be used.
The torque-limiting screwdriver is used for final tightening until clicking
occurs at 4 Nm.

Intraoperative assessment of fracture reduction

Length, alignment, and rotation should be checked clinically. The knee is
taken through a full gentle range of motion to ensure appropriate fracture
fixation. Fracture reduction and fracture fixation are then assessed using AP,
lateral, and oblique x-rays. Specific questions to be answered in this
assessment include:

Is there any sagittal plane deformity?

How satisfactory is the valgus/varus alignment?

The cable method is recommended for checking the alignment of the limb.

Length, alignment, and rotation should also be checked clinically.

How satisfactory is the placement of the LISS fixator on the midlateral
aspect of the tibia?

How satisfactory is the placement of the LISS fixator on the lateral aspect
of the tibial condyle.

Additional screw placement

Removal of the K-wire and insertion of a locking head screw in the most distal plate hole

The most distal locking head screw on the fixator should be inserted last,
just before removal of the insertion guide, in order to ensure the stability of
the construct. The stabilization bolt is then removed and the screw is inserted
through the drill sleeve.

Removal of the insertion guide, and placement of the “A” proximal tibial locking head screw

The insertion guide is then disconnected from the fixator. Insert a locking
head screw or a screw hole inserter into the “A” proximal tibial screw
position.

Intraoperative assessment of fracture stability after fixation
Specific questions to be answered in this assessment include:

Are all of the screws really placed monocortically into the bone, or are
some positioned too far anteriorly or posteriorly?

Are any of the locking head screws in the popliteal fossa and endangering
the popliteal artery? (Although rare, this can occur with excessive anterior
positioning of the fixator or malreduction where the shaft is internally
rotated with respect to the proximal fragment.) This can be assessed
intraoperatively and by image intensification.

It should be checked that self-drilling, self-tapping locking head screws
have not perforated the medial cortex.

Enhancement of LISS stability

Even with the LISS, this unilateral locked plate is rarely enough to deal with an unstable comminuted fracture. A second plate in another plane is advised.